The proposed award is designed to develop the candidate's clinical research skills to prepare him for a career as an independent investigator in the application of motor psychophysics and functional brain imaging to the study of neurological disease. Research Plan: Stroke, Huntington's disease (HD), and Idiopathic Torsion Dystonia (ITD) are diseases that rob people of motor function in the prime of life. Many of the measures of motor performance and functional status commonly used in clinical trials and rehabilitation suffer from subjectivity and lack of scientific validation. The first goal of the proposed study is to characterize and quantify the motor deficit in these diseases using methods previously developed in the study of arm movements in normal subjects. In particular, we will emphasize the importance of examining motor learning abnormalities because we hypothesize that these will give a direct measure of a patient's capacity to compensate or recover from neurological disease. The second goal is to correlate psychophysical parameters of motor performance and motor learning to the degree of expression of brain networks as revealed by functional imaging. This will provide considerable insight into the brain mechanisms underlying abnormalities in motor control. HD and ITD each have an established genetic basis allowing asymptomatic carriers to be identified. Our preliminary studies indicate that these subjects have psychophysical and network abnormalities even though more conventional assessments fail to find any evidence of neurological disturbance. If we confirm and extend these observations, then we will have the tools to follow therapeutic intervention at the earliest stages of disease. In the long term, we hope that our work will lead to the development of a battery of motor tasks that, in conjunction with functional imaging, will be applicable to any neurological disease. This battery will quantify motor deficits; allow monitoring of therapy; provide insight into brain mechanisms: and may serve a rehabilitative function. Educational Plan: By completing this project, I will accomplish six main educational objectives: (1) The design and application of motor psychophysics to neurological disease; (2) Learning PET imaging techniques; (3) The development of skills in brain network analysis and modeling; (4) Learning advanced statistical methods; (5) Learning the principles of functional magnetic resonance imaging; (5) Learning to conduct ethical scientific research, collaborate with colleagues, and produce high quality presentations and publications; and (6) Learning to place experimental findings within their clinical context, and relate them to clinical assessments.